Haproxy conditional logging of HTTP requests

Question

I'm running HAProxy version 3.0.5 for proxying HTTP requests across a bunch of different backends, and also as a TCP proxy for a RabbitMQ cluster. I have added a custom log format so I can better understand the log message at a glance, like so (only the relevant config is here):

global log 127.0.0.1 len 4096 local0 defaults mode http log global option dontlognull option dontlog-normal option log-separate-errors log-format "Client IP:port = [%ci:%cp], Start Time = [%tr], Frontend Name = [%ft], Backend Name = [%b], Backend Server = [%s], Active time of the request = [%Ta ms], Time to establish TCP connection to the server = [%Tc ms], SSL handshake time = [%Th ms], Idle time before the HTTP request = [%Ti ms], Time to get the client's request = [%Tq ms], Time to receive full request = [%TR ms], Response time = [%Tr ms], Total session duration time = [%Tt ms], Status Code = [%ST], Bytes Read = [%B], Termination state = [%ts], Request = [%{+Q}r]" frontend main bind ... listen rabbitmq bind ... mode tcp log-format "Client IP:port = [%ci:%cp], Start Time = [%tr], Frontend Name = [%ft], Backend Name = [%b], Backend Server = [%s], Active time of the request = [%Ta ms], Time to establish TCP connection to the server = [%Tc ms], SSL handshake time = [%Th ms], Idle time before the TCP request = [%Ti ms], Time to get the client's request = [%Tq ms], Time to receive full request = [%TR ms], Response time = [%Tr ms], Total session duration time = [%Tt ms], Bytes Read = [%B], Termination state = [%ts]" 

The rsyslog conf has been simplified to the following to put everything into a single file:

$FileCreateMode 0644 :programname, startswith, "haproxy" -/var/log/haproxy/haproxy.log & ~ 

If I leave it like this, it generates way too much log, over 30 GB a day. So I'd like to log only the failed requests, or maybe even only a portion of the requests. I have seen some examples, but nothing seems to work.

When I try to add the following settings:

defaults option dontlog-normal option log-separate-errors frontend main bind ... http-response set-log-level err if { status ge 400 } listen rabbitmq bind ... tcp-request content set-log-level silent unless { rand(100) lt 10 } 

Now it logs nothing. Even though I generate correct and failed requests, and there are rabbitmq messages as well, nothing is logged.

Answer 1

Actually I ended up being dumb... I didn't realize that 404 response, if coming from a backend, is considered "normal" in HAProxy and I had option dontlog-normal which suppressed it, and I tried testing it that way... I ended up removing the dontlog-normal, setting the log level to silent by default, and setting it to notice for ~10% of requests, and err for all failed requests:

frontend main bind ... http-response set-log-level silent http-response set-log-level notice if { rand(100) lt 10 } http-response set-log-level err if { status -m int 400:599 }